Snow skis may be considered to be comprised of a body portion and a base or running surface portion. Typically, the body portion is formed of a composite of fiberglass impregnated with epoxy resin, a core material of foam, wood or honeycomb metal, and other materials which may be included in the ski body to control ski vibration or otherwise affect ski performance. The present invention also has application to skis whose body portion is formed in any other way. The base or running surface portion of the ski is typically comprised of a layer of petroleum based material such as polyethylene, high molecular weight sintered material, or P-tex,.RTM. all of which materials are characterized by the ability to run freely on a snow surface rather than sticking to it. The lateral outer portions of the base surface are provided with metal edges which extend from tip to tail on both sides of the ski and, when sharp, provide an edge which allows a user to carve turns and check his speed, particularly on hard packed snow or icy surfaces. Metal ski edges typically include a rectangular portion having a surface exposed on the bottom, or running surface of the ski, a surface exposed along the lower portion of the lateral side of the ski, and an arm extending from the rectangular portion into the body of the ski above the slippery base member to anchor the metal ski edge in place. Metal ski edges may be continuous or "cracked" to increase their flexibility, or in some instances, particularly in older skis, may be formed of a plurality of longitudinally adjacent separate metal members.
In the past, ski edges have been turned or sharpened by grinding, filing or sanding in such a manner that the outer, lower corner of the ski edge defines an angle of approximately 90.degree.. With use, however, the corners of metal ski edges become rounded or dull thus reducing the skier's ability to control the movement of his skis over the surface of the snow, and particularly over icy or hard packed snow. Forming ski edges entirely out of extremely hard, brittle steel has not proven to be a solution to the wear problem, both due to difficulty of manufacture and because the continuous flexing of a ski edge during use causes brittle material to crack.
It is known to attempt to reduce the rapid dulling of a metal ski edge by coating the surface of the metal ski edge, or a portion thereof, with a harder material. For example, French patent disclosure No. 1,563,297 discloses placement of a thin layer of tungsten carbide or aluminum oxide on either the side or bottom surface of a metal ski edge. The disclosed method of applying the material is flame spraying, a process wherein a flame, such as from a blow torch, is directed against the surface to be coated, and particles of the material to be applied are then directed into the flame and carried against and bonded to the metal ski edge surface by the movement of the flame.
Stugger et al. U.S. Pat. No. 3,918,728 discloses the use of what is termed "cold process" flame spraying to apply carbide particles of a particular size range, i.e., between -100 mesh and 15 microns, to the lateral surface of a metal ski edge in a layer of from 1-10 mils thickness to roughen the surface and make it abrasive.
Applicant has found that the use of flame spraying is not an effective or commercially satisfactory technique for use with skis into which the metal edge has already been incorporated in that it is difficult to prevent the flame sprayed material from being deposited on the ski as well as on the metal ski edge. In the present invention, the carbide is actually drawn toward the metal ski edge during the electrical discharge as will be described hereafter. Flame spraying of metal edges prior to installation on a ski also creates complications related to sanding and finishing the bottom of the ski surface.
It is also known generally to deposit precious metal on a substrate by sparks discharge. Belopitov, U.S. Pat. Nos. 3,028,478; 3,446,932 and 3,523,171 all disclose apparatus for accomplishing this. The '932 and '171 patents disclose apparatus wherein an anode in the shape of a rapidly rotating thin disc or brush are charged and brought into pressure contact with a cathode material to be coated.
The present invention provides a unique continuous coating method and apparatus for treating a metal ski edge after it is mounted in a ski whereby a very thin, melted coating of hard material is deposited electrically on the lateral sides of the metal ski edge. The method and apparatus deposits a relatively smooth melted coating of material such as tungsten carbide without undue heating, discoloring or otherwise damaging any portion of the ski adjacent the metal ski edge. In particular the method and apparatus deposits a hard melted coating without the roughness characterized by the prior flame spray coating techniques wherein distinct particles were deposited on the metal ski edge.